This invention relates to a control device for controlling a controlled circuit included in an electric apparatus supplied with power from an A.C. source, and more particularly, to a control device for an electric apparatus which prevents the controlled circuit from being abnormally controlled after the recovery from a momentary power failure of the A.C. source.
With an electric apparatus, for example, an electric rice-cooking apparatus, a heater is connected between the terminals of a commercial A.C. source through a switching element such as a relay switch or triac. The operation of the switching element is sequentially controlled by an output signal from a control device. However, when a momentary power failure takes place in the A.C. source, the controlling steps of the control device supplied with power from the A.C. source are initialized, thereby suspending the sequential control of the switching element. Thus, after the recovery of the power failure of the A.C. source the sequential control for the switching element sometimes has to be performed from the starting point. This leads to abnormal operation of the rice-cooking apparatus. The conventional process intended to suppress this abnormal operation comprises the steps of connecting a capacitor as an auxiliary power source to control lines through which power is supplied to the control device and, upon the momentary power failure of the A.C. source, discharging the capacitor to hold the control device in a conducting state, thereby preventing the control device from being initialized. However, the above-mentioned conventional process has the drawback that, since power is also supplied from the capacitor to a coil for energizing the relay switch, the capacitor must have a large capacity in order to act as an auxiliary power source, thus presenting difficulties in miniaturizing an electric apparatus, for example, a rice-cooking apparatus.